1. Field of the Invention
The present invention is in the field of spas and more particularly relates to a method for controlling the heating cycle of a spa that keeps the spa at a ready-to-use temperature with a minimum of human intervention.
2. The Prior Art
The type of spa with which the system of the present invention is intended to be used is typically several times larger than a bathtub. Frequently, the spa is located outdoors and is provided with its own heater and pumps for heating and circulating hot water. To maintain the cleanliness of the water, the spa is equipped with a filter and filter pump that draws water from the spa, passes it through a filter, and returns it to the spa.
Spas vary widely in the manner in which the various functions are coordinated. In some spas, the operator must initiate each function, while other spas are programmed to provide various water temperatures at specified times.
In U.S. Pat. No. 4,780,197 issued Oct. 25, 1988, Schuman describes a filtration system in which the pump normally operates on a daily ON-OFF cycle determined by an adjustable timer.
In U.S. Pat. No. 4,233,694 issued Nov. 18, 1980 to Janosko et al., there is described a control system for a spa that protects the heater against overheating when the water level has fallen and in which operation of both the filter pump and the heater are initiated by the user. In U.S. Pat. No. 5,585,025 issued Dec. 17, 1996, Idland describes a spa control circuit that includes protection against overheating. The control system includes a single thermometer that detects the temperature of the spa water. The temperature is supplied to a thermostat that uses an ON-OFF control mode to maintain water temperature between normal operating limits.
In U.S. Pat. No. 5,559,720 issued Sep. 24, 1976, Tompkins et al., describe a spa control system that uses a microprocessor and that begins to warm the water in advance of actual use.
In U.S. Pat. No. 5,079,784 issued Jan. 14, 1992, Rist et al., describe a control system that uses a proportional mode of control in which the current to the heater is reduced as the temperature approaches the temperature set on the thermostat. The system also includes a safety circuit that prevents operation of the heater unless the pump is circulating water.
Although some individual features of the present invention can be found in the prior art, the overall system of the present invention and its mode of operation appear to be unknown.